Dates: 25 August-8 September Coverage: Commentary every day from 18:00 or 18:30 BST on BBC Radio 5 live sports extra

Britain's Andy Murray said he was disappointed that Novak Djokovic proved physically stronger in their US Open quarter-final.

The 27-year-old lost 7-6 (7-1) 6-7 (1-7) 6-2 6-4 over three hours and 32 minutes at Flushing Meadows.

"I thought physically he was better than me in the end," said Murray, the eighth seed.

"I was a little bit disappointed, to be honest, because I did train very hard."

Murray carried out a training block with his support team in Florida after a disappointing quarter-final defeat at Wimbledon in July.

"You do the work for these matches, so I would have liked to have felt a little bit better towards the end," said the Scot.

Djokovic, 27, also felt he had an advantage when he faces Murray in Grand Slam matches over the best of five sets.

"I get the feeling that if I get to stay with him and work, and not get too loose and too frustrated with points, and not allow him to get into a big lead, I feel like there is a point where I have that edge physically," said the Serb.

"That's what I try to always focus on and it paid off tonight."

BBC tennis correspondent Russell Fuller's analysis

"Murray has provided the most compelling evidence of the year here in New York that 2015 should have much to offer, but Djokovic remains out of reach for now. Murray matched the world number one throughout the first two sets, but Djokovic was the stronger physically, and both Murray's serve and his speed around the court dropped noticeably as the match moved into a fourth set. Qualifying for the end-of-season World Tour Finals didn't seem to be an immediate priority, but Murray does have three more tournaments to clinch one of the eight qualifying spots."

Murray, who underwent back surgery following last year's US Open and missed the final months of the 2013 season, described playing Djokovic as extremely demanding.

The Briton has made at least the quarter-finals of all four Grand Slams this year, but found the world number one a step too far.

"Maybe I haven't played enough matches at that level this year," he said.

"It's obviously different playing at that level, playing against the number one in the world. And the way that we play against each other, it's just an extremely physical match.

Murray said that in games against other players, for example Roger Federer, the points come quicker and it is not as demanding.

He added: "When me and Novak play against each other, you obviously see very tight, long rallies. Both of us do a lot of running.

"Maybe I'll gain a lot from playing a match like today, because it doesn't matter how much training you do, when you get on the match court it's different.

"I can't practise with the best player in the world, so it's tough to practise at that intensity."

Murray had spent three-and-a-half hours longer on court than Djokovic on his way to the last eight

Murray needed treatment from the trainer in the fourth set but played down the issue.

"I got stiff in my hips and my back towards the end of the third set," he said. "I don't know exactly why. I'm certainly not injured. I didn't hurt anything.

"It was just fatigue I think and I stiffened up towards the end of the third set."